You have it switched. It was Han that said "I love you" and Leia "I know". Leia got injured during their attack on the power shield generator, and Han crouched over her to make sure she was okay when an imperial officer (i think it was a stormtrooper) told han to stand up. Leia showed Han she still had her blaster and that's when Han said, "I love you." Leia replied with "I know."

i have a few favorites, though the dramatic often beat the comedic ones for me

the crazed Anakin on mustafar, i think i actually love this entire dialogue, but i'll shorten it

Padme- Obi-Wan was right! you've changed!Anakin- I don't wanna here anything about Obi-Wan, the Jedi turned against me, don't you turn against me!Padme- I don't know you anymore!

-when Anakin sees Obi-Wan at the top of the stairs-Anakin- Liar!!!Padme- -Looks around, and sees Obi-Wan- No!Anakin- You're with him, you brought him here to kill me! -starts to strangle Padme-Obi-Wan- Let her go Anakin!-Anakin continues the strangling-Obi-Wan- Let her go!-Anakin stops-Anakin- You turned her against me!Obi-Wan- You have done that yourself!

-when Obi-Wan has cut off Anakin's legs-Obi-Wan- You were the Chosen One!You were send to destroy the Sith not join them!Bring balance to the Force, not leave it in darkness!Anakin- I hate you!Obi-Wan- You were my brother Anakin, I loved you!Anakin- -Screaming of pain-

And there are some small ones

Mace Windu against the 'dying' Palpatine:"I'm going to end this once, and for all!"

Han Solo on the Desert Skiff"My sight's getting better, instead of one big black spot, i now see one big white spot."